std::fixed, std::scientific, std::hexfloat, std::defaultfloat

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< cpp | io | manip

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C++
 
输入/输出库
I / O操纵
C-风格的I / O
缓冲区
Original:
Buffers
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basic_streambuf
basic_filebuf
basic_stringbuf
strstreambuf（过时了）
流
Original:
Streams
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抽象
Original:
Abstractions
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ios_base
basic_ios
basic_istream
basic_ostream
basic_iostream
文件I / O
Original:
File I/O
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basic_ifstream
basic_ofstream
basic_fstream
字符串I / O
Original:
String I/O
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basic_istringstream
basic_ostringstream
basic_stringstream
阵列的I / O
Original:
Array I/O
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istrstream（过时了）
ostrstream（过时了）
strstream（过时了）
类型
Original:
Types
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streamoff
streamsize
fpos
Error类的接口
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Error category interface
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iostream_category（C++11）
io_errc（C++11）
 
输入/输出操纵
浮点格式
Original:
Floating-point formatting
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fixed
scientific
hexfloat
defaultfloat

（C++11）
（C++11）
整型格式
Original:
Integer formatting
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布尔格式
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Boolean formatting
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boolalpha
noboolalpha
场的宽度和填充控制
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Field width and fill control
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其他格式
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Other formatting
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空白处理
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Whitespace processing
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输出冲洗
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Output flushing
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状态标志位操作
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Status flags manipulation
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时间和金钱I / O
Original:
Time and money I/O
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get_money（C++11）
get_time（C++11）
put_money（C++11）
put_time（C++11）
 
Defined in header <ios>
(1)
std::ios_base& scientific( std::ios_base& str );
 (2)
std::ios_base& hexfloat( std::ios_base& str );
 (3) （C++11 起）
std::ios_base& defaultfloat( std::ios_base& str );
 (4) （C++11 起）
修改默认的格式为浮点I / O
Original:
Modifies the default formatting for floating-point I/O
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1)
设置floatfield的流strfixed仿佛通过调用str.setf(std::ios_base::fixed, std::ios_base::floatfield)
Original:
sets the floatfield of the stream str to fixed as if by calling str.setf(std::ios_base::fixed, std::ios_base::floatfield)
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2)
设置floatfield的流strscientific仿佛通过调用str.setf(std::ios_base::scientific, std::ios_base::floatfield)
Original:
sets the floatfield of the stream str to scientific as if by calling str.setf(std::ios_base::scientific, std::ios_base::floatfield)
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3)
设置basefield的流strfixedscientific同时，如果通过调用str.setf(std::ios_base::fixed | std::ios_base::scientific, std::ios_base::floatfield)。这使得十六进制浮点格式.
Original:
sets the basefield of the stream str to fixed and scientific simultaneously as if by calling str.setf(std::ios_base::fixed | std::ios_base::scientific, std::ios_base::floatfield). This enables hexadecimal floating-point formatting.
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4)
设置basefield为零的流str，如果通过调用str.unsetf(std::ios_base::floatfield)。这使得缺省浮点的格式，这是固定的和科学的不同从.
Original:
sets the basefield of the stream str to zero, as if by calling str.unsetf(std::ios_base::floatfield). This enables the default floating-point formatting, which is different from fixed and scientific.
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这是一个I / O操纵器，它可被称为与表达式如out << std::fixed类型out任何std::basic_ostream，或与一个表达式如in >> std::scientific类型in任何std::basic_istream.
Original:
This is an I/O manipulator, it may be called with an expression such as out << std::fixed for any out of type std::basic_ostream or with an expression such as in >> std::scientific for any in of type std::basic_istream.
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目录

[编辑] 参数

str -
参考I / O流
Original:
reference to I/O stream
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[编辑] 返回值

str（参考操作后到流）
Original:
str (reference to the stream after manipulation)
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[编辑] 为例

#include <iostream>
#include <sstream>
int main()
{
    std::cout << "The number 0.01 in fixed:      " << std::fixed << 0.01 << '\n'
              << "The number 0.01 in scientific: " << std::scientific << 0.01 << '\n'
              << "The number 0.01 in hexfloat:   " << std::hexfloat << 0.01 << '\n'
              << "The number 0.01 in default:    " << std::defaultfloat << 0.01 << '\n';
    double f;
    std::istringstream("0x1P-1022") >> std::hexfloat >> f;
    std::cout << "Parsing 0x1P-1022 as hex gives " << f << '\n';
}

Output: 

The number 0.01 in fixed:      0.010000
The number 0.01 in scientific: 1.000000e-02
The number 0.01 in hexfloat:   0x1.47ae147ae147bp-7
The number 0.01 in default:    0.01
Parsing 0x1P-1022 as hex gives 2.22507e-308

[编辑] 另请参阅
改变浮点精度
Original:
changes floating-point precision
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（函数） [edit]
来自“http://zh.cppreference.com/mwiki/index.php?title=cpp/io/manip/fixed&oldid=27401”